Conventionally, various apparatuses, methods, and the like have been proposed which estimate whether or not there is a possibility that a vehicle will collide with an oncoming vehicle travelling on an oncoming lane. For example, a vehicle collision preventing apparatus below is disclosed (see Patent Literature 1). That is, first, the position of the vehicle as it will be after a predetermined time is estimated, and the veering-off amount into the oncoming lane at that time is calculated. Next, if the veering-off estimation amount of the vehicle is equal to or larger than a predetermined value, a safety inter-vehicle distance of those vehicles is calculated which, when they decelerate at respective predetermined decelerations, allows the relative velocity therebetween to be a predetermined velocity just before collision. If the inter-vehicle distance therebetween is smaller than the safety inter-vehicle distance at the present moment, it is estimated that there is a possibility that they will collide.